Apparatus for sorting granular materials



Dec. 10, 1940. D. c. TURNBULL APPARATUS FOR SOR'I'ING GRANULAR MATERIALS 3 Sheets-Sheet 1 Filed Aug. 20, 1938 INVENTOR c102 ATTORNEY Dec. 10, 1940. D Q TU N L 2,224,169

APPARATUS FOR SORTING GRANULAR MATERIALS Filed Aug. 20, 1938 3 Sheets-Sheet 2 INVENTOR M Qc/ 5 ATTORNEY DQQ 1940' D. c. TURNBULL J APPARATUS FOR SORTING G-RA NULAR MATERIALS Filed Aug 20, 19:58, 3 Sheets-Sheet s INVENTOR ATTORNEY Patented Dec.10,-1940 v PATENT OFFICE I 2,224,169 APPARATUS FOR SOB-TING GRANULAR MATERIALS David C. Turnbull, Mishawaka, Ind., assignor to The American Foundry Equipment Company, Mishawaka, Ind, a corporation of Delaware Application August 20, 1938, Serial No. 225,850

7 Claims.

This inventionrelate's generally to apparatus for sorting granular materials and more particularly to the separation of mixed solid particles of different weights and densities.

In various operations wherein granular material is involved, it is often necessary or desirable to separate and sort the material in accordance with the size or weight of the particles. One example of such separation is the reconditioning of 10 granular abrading material employed in abrasive cleaning of forgings, castings or other metal members, which abrading material usually consists of round steel shot, cracked steel grits, sharp quartz sand or similar material. In the course of operation the abrading material becomes mixed with core sand, scale, rust, dust, and other foreign matter, which it is desirable to remove from the abrading material. The present invention is particularly adapted for reconditioning 2o abrading material and in the present illustrative embodiment of the invention is described in connection with reconditioning abrading material for the cleaning or surface treating of metal castings, forgings, bars, sheets and the like.

35 In accordance with the present invention, the material to be sorted is urged along a supporting surface and thereafter is allowed to fall freely from the surface and a fluid current is drawn through the stream to entrain the lighter and 30 finer particles and separate them from the heavier particles. The heavier particles are immediately isolated from the fluid current carrying the lighter particles and are collected. After separation of the heavier particles the fluid our- 35 rent with the lighter. particles entrained therein preferably is caused to change direction abruptly whereby the particles are thrown out of the stream and can be collected. If desired, an electrostatic charge may be imparted to the 40 lighter particles of dust or sand while on the supporting surface to retard their removal therefrom, thereby to produce a further separating effect.

The invention also provides novel apparatus 45 for carrying out the invention, which apparatus, according to an illustrative embodiment of the invention, comprises a housing having a rotatable table or spinner therein, onto which the granular material is deposited. The table is 5 rotated to cause the material to travel outwardly thereon and finally drop off across the peripheral edge. A fluid current is drawn through the material as it falls from the table or spinner, which current entrains the finer and lighter 55 particles and carries them inwardly away from the remainder of the particles. A baflle structure is disposed in cooperative relation to the table or spinner and serves both to segregate the entrained particles from the heavier particles and to direct the flow of the fluid material. Baille means are provided for effecting one or more abrupt changes of direction of the fluid current after it has passed through the falling material, and entrained the lighter solids, thereby to throw out the entrained solids. If desired, one or more 10 settling chambers may be provided for effecting selective settling out of entrained particles of various sizes. Suitable means, such as a felt pad rubbing against the table, may be provided for producing or enhancing an electrostatic charge 15 on the table whereby to electrostatically charge the finer particles such as sand and dust as they travel along the table and thereby to retard their removal from the table.

An object of the present invention is the provision of an improved apparatus for sorting granular material wherein particles of various sizes can be accurately and easily separated and segregated.

Another object of the invention is to provide an apparatus for reconditioning abrading material employed in cleaning metal forging's, cast ings and the like, in order to remove included sand, scale, dust and other foreign matter whereby the abradant is suitable for repeated use.

Another object of the invention is the provision of apparatus for separating solid particles of various sizes, which apparatus is simple, eflicient, rugged, operates with a relatively low power consumption, and which is relatively com- 5 pact and eflicient as to space.

Still another object of the invention is the provision of apparatus for cleaning or treating abradant material to remove large foreign articles such as sand, dust, scale or other foreign matter 40 to efficiently recondition the abrasive material for reuse.

Still another object of the invention is the provision of apparatus for separating solid "particles in accordance with the size or weight wherein a plurality of separations can be carried out in the course of a single cycle.

Various other features and advantages of the invention will be apparent from the following tive forms of construction, reference being had to the accompanying drawings, wherein Fig. 1 is a fragmentary side elevational view of apparatus for abrasive blast cleaning and embodying one form of separator mechanism con- .structed in accordance with the invention in. com- In the following description and in the claims,

various details will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit. Like reference characters denote like parts in the several figures of the drawings.

Referring now particularly to Fig. 1, there is illustrated a cleaning chamber or cabinet I having associated therewith an abrasive throwing wheel 2 of the rotary centrifugal type, driven by a motor 3 and adapted to project a stream of abrading material at abrading velocities against articles to be cleaned, such as metal castings, forgings, bars, billets, sheets and the like. The articles are supported within the chamber in the stream or conveyed therethrough by suitable supporting or conveying means (not shown). Abrading material is delivered to the wheel 2 from a hopper 4 hereinafter more fully described, which discharges into a feed conduit 5 leading to a feed pipe 6, which latter delivers the abrasive operatively to the throwing wheel 2 in a manner which will be understood by those skilled in the art.

Spent abrading material, together with debris such as core sand, scale, rust, dust and other foreign matter, is collected in a hopper I from which it flows by gravity or by a suitable conveyor (not shown) to an elevator housing I0 having therein an elevator II comprising endless chains or belts I2 carrying buckets I3, and trained over drums or pulleys I4, I4 supported at the top and bottom of the housing III as by shafts I5, I5. The elevator is driven as by a motor I6 connected by a suitable drive II to one of the upper shafts I5.

The abrading material is delivered from the elevator II to a coarse separator or screening mechanism 20 adapted to remove any nuts, bolts, large pieces of scale, broken pieces of castings or other foreign articles of relatively large size, .such as may be mixed with the abrading material as it comes from the cleaning chamber.

The screening mechanism 20 has an inlet pas- I sage 25 leading from the elevator housing ID to a chamber 26 having a generally cylindrical screen 30 therein. A conveyor screw 21 is disposed in the inlet passage 25, and extends from adjacent the elevator housing to within the chamber 26, and a screw 28 is disposed within the chamber 26 and inside of the screen 30. The screen 36 may befixed in the housing 26 but preferably is mounted for rotation with the screw 28. The screws 21 and 28 are carried by a shaft 29 for rotation, which shaft is rotated by a drive 3| connected to the shaft I5.

When the shaft 23 is rotated the screws 21 and 28, together with the cylindrical screen 30, are

rotated and feed abrading material and foreign matter through the separator". The abrading material and fine particles pass through. the screen 30 and drop into a discharge conduit 33 and the larger particles are carried to the end of the screen 30 and are discharged from the chamber 26 through a debris conduit 32.

The discharge conduit 33 extends to a feed inlet 34 of a granular material separator 50, shown more particularly in Fig. 3, to which reference now is made. It will be understood that where the separator is used in connection with apparatus of other types than that shown, the granular material to be separated will be delivered in a suitable manner to the feed inlet 34.

The separator 50, shown more in detail in Fig. 3, comprises a housing 5|, preferably supported above the cleaning chamber I as by a suitable frame 52. The housing defines a separating chainber 5I, below which is a hopper 4 which may, if desired, be defined by the lower wall portions of the housing 5|. The housing has an inlet 34 in the upper wall and a discharge outlet 56 in the hopper 4.

Rotatably disposed in the chamber 51, preferably adjacent and under the inlet 34, is a spinner or table preferably of circular form and having at its periphery a downwardly and outwardly projecting apron 8|- The table 88 is supported for rotation by a shaft 83, a hub 84 preferably being provided for supporting the table 80 on the shaft 83. The shaft extends through the top wall of the housing and is journaled in bearings and 81 suitably supported on a frame 88. The shaft is rotatably driven from the shaft 23 (see Figs. 1 and 2) of the screening separator 20 by a drive 35 which drives a shaft 36 carrying a gear 31 which meshes with a gear 38 carried on the shaft 83.

Disposed in the chamber 51, below the rotatable table 80, is a baille unit 60 adapted to cooperate with the table 80 in separating the granular material. The baille unit comprises an outer, and preferably cylindrical, baflle 6| cooperating with a hopper 62 to define an outer or heavy dust settling chamber I03. The baflle 6| may extend upwardly to short of the outer edge of the apron 8|, a gap or passage 98 being provided of sufficient vertical extent to permit the passage of an air stream. In certain cases it is desirable that the edge of the apron 8| terminate inwardly short of the top of the baille 6|, as illustrated in Fig. 3. It is preferable that the top of the center baffle be formed as a separate skimmer ring I3, which is mounted adjacent and preferably on the top edge of the wall forming the baffle 6|.

The skimmer ring I0 is of generally annular form and preferably is provided with an upper edge of tapered form. The skimmer ring I0 may comprise a cylindrical ring II and an annular ring I3 secured together or a single member of angular cross-section. A cover member 12 of an abrasion-resisting material is secured to the members II and I3 as by welding and may have a depending apron I4 adapted to extend below the top edge of the baille 6 I.

The skimmer ring I0 is supported, as by bolts I5, which extend through the wall of the housing 5| and through the upright portion of the ring III. The bolts I5 preferably are resiliently connected to the skimmer ring as by nuts I6 and pressure springs 11, and are adjustably positioned by adjusting nuts I8. The skimmer ring I0 thus can be adjusted in a horizontal direction so that its upper edge is centered with respect to the outer edge of the table and the gap or passage 98 can be made uniform throughout its entire extent.

The vertical extent of the gap 98 can be adjusted vertically by adjusting either the table 80, or the skimmer ring 10, or both. For example, the table 80 can be adjusted by suitable adjustment of the hub 84 on the shaft 83. On the other hand, the skimmer ring I0 may be adjusted by providing for vertical adjustment of the bolts 18 in the housing 5|, as for example, by providing slots (not shown) in the housing. In this connection it will be noted that the apron I4 cooperates with the bafile GI and extends across any space or gap which may result from elevating the skimmer ring 10 relative to the baffle 6|.

Preferably one or more additional bai'lles are disposed within the bailie 6| in order to cause the air passing into the chamber to travel in a tortuous path therein. In the present example, two additional baflles are provided, namely, an intermediate baflle 65 and an inner baille 66, enclosing respectively an intermediate chamber I05 and an inner or light dust settling chamber I06 generally concentric with each other and with the chamber I03. The chamber I05 is open at the bottom, but is closed at the top to prevent the passage of the air stream. The top may be closed'by extending the baille 65 to the table 80 but preferably a flange or apron 82 depends from the table 80 and cooperates with the bafiie 65 to close the top of the chamber I 05.

The chamber I06 defined by the baffle 66 is open at the top but is partially closed at the bottom by a hopper 61 having an opening 69 communicating with the lower portion of the chamber I03.

The 'baiile unit 60 preferably is supported by a plurality of bolts 68 which extend radially through the walls of the housing 5| and the baffies 6|, 85 and 66. These bolts carry suitable nuts, some of which position and secure the bolts relative to the housing and others of which position the respective ballles on the bolts.

Extending from the inner or light dust settling chamber I 06 through the baffles 65, 66 and BI and through the wall of the housing 5| is an air outlet conduit which communicates with the casing of a blower fan 92 either directly or through an outlet pipe 9|. The blower fan 92 is suitably mounted as by a bracket 93 and is rotated by a motor 94. The outlet of the blower fan is connected to a conduit 95 which leads to an equalizing chamber 96 which communicates with a plurality of air inlets leading into the separating chamber 51, preferably through the upper wall and above the rotatable table.

When the blower fan 92 is driven it circulates a relatively strong current of air through the conduit 95, the equalizing chamber 66, air inlets 91 and into the separating chamber 51. A current of air passes from the separating chamber 51 through the gap 98 and into the outer settling chamber I03 and then successively through the chambers I05 and I06 in alternate directions. Finally the air is discharged through the conduit 90 and outlet pipe 9 I.

The operation of the separator is as follows:

The shaft 36 is driven to rotate the shaft 83 which carries the table 80. The blower fan 92 is driven to circulate an air stream as above described- The granular material to be separated is introduced into the housing 5| through the inlet 34 and drops onto the table 80. Rotation of the table 80 causes the granular material to be carried outwardly and to be thrown off the apron 8I in a falling shower or stream.

The larger and heavier particles are thrown outwardly by a greater centrifugal force than the lighter particles and are deflected by the skimmer ring I0 and drop intdthe hopper I, from whence they are withdrawn through the conduit 5.

The lighter particles travel outwardly along the table 80, but, owing to their lesser momentum are not thrown outwardly off the table with as much force as the heavier particles. The lighter particles drop off the apron 8| and the air stream passing through the stream or shower of particles entrains the lighter particles and carries them through the gap 98 and into the chamber I03, thus separating them from the heavier particles.0wing to their greater momentum the heavier particles .are not entrained by the air stream but fall outside of the skimmer ring.

The downward movement of the air in the outer or heavy dust settling chamber I03, causes the entrained particles to be carried downwardly and, when the air stream changes direction abruptly and passes into the intermediate chamber I05, the heavier of the entrained particles are thrown out of the stream and fall into the hopper 62. The air stream then passes through the chamber I05 and, after again reversing its direction, passes into the inner or light dust settling chamber I06. Any fine particles which may be carried into the inner chamber I06 are thrown out, either by the abrupt change of the direction of the air current at the top of the chamber or the change in direction occurring when the air passes into the outlet passage I01. ticles drop. through the opening 69 into the collecting hopper 62.

Where a separator, such as that described herein, is employed in a system for reconditioning abrading material, the operation of the separator is substantially as above described. In this case the lighter particles will generally comprise sand, dust, small particles of scale or rust and other foreign matter, and the heavier particles will generally comprise the abrading material.

The operation of the complete abrading material reconditioning apparatus illustrated in Figs. 1 to 4 and described hereinbefore, is as follows:

Abrading material is supplied from the hopper 4 through the conduit 5 and the feed pipe 6 to the throwing wheel 2. The latter projects the abrading material at abrading velocities against the metal forgings, castings, bars, sheets or other articles to be cleaned.

Spent abrasive, together with dust, scale, sand, broken casting parts, nuts, bolts and other debris are collected in the hopper I and lifted therefrom by'the elevator II and deposited in the separator 20. Th rotation of the screws 21 and 28 advances the mixed material into the screen 30 and causes the finer components, such as abrading material, dust, sand, etc. to pass through the screen. The larger components, such as nuts, bolts, broken casting parts, large chunks of scale, etc. will not pass through the screen but are discharged from the end of the screen and pass out through the debris outlet 32.

The finer components drop into the discharge outlet 33 and pass through the inlet 34 into the separator 50. The separator 50 operates as above described to separate the abrasive particles from the dust, sand, etc. the former being returned These parto the hopper 4 and the latter being discharged through the discharge conduit 54.

It has been found that, in certain cases the sand and dust on the table have an electrostatic charge induced therein which causes these particles to be attracted by the table and retards their movement along and off the table. The particles of abrading material are not retarded and therefore fiow off the table with a greater velocity whereby there is an inherent tendency for the latter -to separate from the dust and sand as they leave the table.

In some cases it is advantageous to enhance this electrostatic effect and this can be accomplished by insulating the table and causing the table to rub against a member of such material as will charge the table as it rotates, which action induces an electrostatic charge in the particles of dust and sand.

Referring particularly to Fig. 4, one or more.

friction members is secured to the home 65 in position to bear frictionally against the flange 82 as the table is rotated. The friction member I20 is formed of material which upon rubbing against the flange 82 will produce an electrostatic charge against the table 80 and for example, may comprise a ring or strip of felt. The friction member I20 preferably may be secured to the baffle 55 by one or more bolts I2I and preferably is folded over as illustrated so as to press resiliently against the flange 02.

The table 80 is insulated from the shaft 03 by an insulating bushing I22, for example, which may have a flange I23 which insulates the table .from the hub 04. If desired, a protector ring I23 may be fitted on the shaft 83 above the bushing I22 to prevent the dropping material from causing undue wear of the bushing I22.

Various modifications may be made in the invention above described and a second embodiment of separator is illustrated in Figs. 4 and 5 to which reference now is made.

The separator 200 includes a housing 20I defining a separating chamber 204 below which is a storage hopper 202 for collecting separated heavier particles. A charging inlet 250 leads into the upper portion of the housing 20I and communicates with an abrasive hopper 25I having a discharge opening 25I'. The abrasive hopper 25! preferably is of generally conical form as illustrated.

Disposed in the separating chamber 204, preferably closely below the discharge outlet 255 of the abrasive hopper 25I, is a spinner or table 220 having at its periphery a downwardly and outwardly extending apron 221. The table 220 is carried for rotation by the shaft 22I, the table being secured to the shaft as by a hub 222 and pin 223; the table 220 may be vertically adjustable on the sha'ft for the purpose of adjusting the width of the air stream gap hereinafter described. The shaft 22I is rotatably mounted in bearings 224 and 225 carried by a bracket 226 and is rotated from a shaft 260 by suitable gears 26I and 262, the shaft 260 being driven from a suitable source of power not shown.

Disposed in the separating chamber .204 is a baflie unit 2I0 comprising an outer wall or bafile 2II defining an outer chamber 2H, an intermediate wall or baffle 2I4 defining an intermediate chamber 2I8 and an inner wall or wall baffle 2| 5 defining an inner chamber 2I9. Extending below the outer chamber 2I'I and. intermediate chamber 2| 8 is a hopper 2I2 having a discharge spout 2 I3 extending through the lower wall 280 of the hopper 202. Extending below the inner chamber 2I9 is a hopper 240 which preferably is provided with a discharge spout 24I which may extend in the discharge conduit 2I3 a substantial distance for the purpose of reducing or eliminating any back draft. The discharge spouts 2I3 and 24I may lead to a sand box or boxes (not shown) and preferably are closed by a flap valve or gate (not shown) which is yieldingly held in closed position so as to remain closed except when forced open by accumulated sand in the spouts.

The outer baflle 2 extends to a point substantially under the outer rim of the apron 221 but spacedtherefrom to provide an air stream 242. The width of the gap can be adjusted by vertical adjustment of the table 220 in the shaft Preferably, the top portion of the baflie 2| I is formed as or carries a skimmer ring 243 which may be replaceable and which is formed of good wear-resisting material. The top edge of the skimmer ring preferably is thinned or tapered.

The intermediate bafile 2I4 may extend sub-- stantially to the table 220 to provide a closure between the chambers 2I'I and 2I8 at the top or if desired, a flange 220 may extend downwardly from the table in telescoping relation with the baffle 2I4 for the purpose of closing'this.

space.

The baille 2I5 is spaced from the table to permit the passage of an air stream fromchamber 2I0 to chamber 2I9. Thus it will be seen that an air stream can flow from the separating chamber 204 through the gap 242 downwardly through the chamber 2I'I, upwardly to the chamher 2! and downwardly into the chamber 2I9.

An outlet duct 230 extends from the inner chamber 2I9 through the baffles 2I5, 2I4 and 2H and through the side wall of the housing 20I for the purpose of conducting an air stream from the inner chamber. The outlet duct extends to the casing of a blower fan 232 and may be provided with a gate or valve 254 for controlling the fiow of air. The blower fan 232 is suitably mounted as by a frame 233 and is driven by a suitable source of power such as a motor 234. The outlet of the blower fan 232 is connected by a conduit or duct to an inlet 236 in the wall of the housing 20l.

The baflies 2II, 2I4 and 2I5 are suitably supported within the housing in properly spaced relation. These members may conveniently be supported by securing them to the outlet duct 230, as by welding. The outer baffle 2 may be additionally supported by securing the discharge spout 2I3 to the lower wall 280 of the hopper 202. If desired, additional supporting and spacing means (not shown) for the baffles may be provided.

Cooperating with the hopper 25! is a bafile 253 which preferably is of conical form and which, with the upper portion of the hopper 25I and the adjacent portion of the housing 20I, defines a wind box or chamber 254 in the upper portion of the housing 20I.

The operation of the apparatus illustrated in Figs. 5 and 6 is as follows:

The shaft 260 is suitably driven to drive the shaft 22I and thereby rotate the table or spinner 220. The motor 234 is energized to drive the blower fan 232 and thereby cause a stream of air to flow serially through the duct 235, wind box 254, gap 242, chambers 2I'I, 2I8, 2I9 and duct 230.

Granular material to be separated is introduced into the housing IN to the charging inlet 250 and flows from the hQpper l through the opening 255 and is deposited on the rotating table 220. The granular material is urged outwardly along the table and finally drops off the outer rim of' the apron 221. The larger and heavier particles have a greater momentum imparted thereto and are thrown outwardly with greater force than the lighter particles.

An air stream enters the wind box in a generally tangential direction and then flows from the wind box into the separating chamber 204 and through the stream of falling material and entrains the lighter particles and carries them into the chamber 2 II. The baflie 253 prevents the air stream from agitating the granular material which is on the table and directs the air stream through the falling stream of granular material. The air stream changes direction abruptly in passing from the outer chamber 2|! to the intermediate chamber 2| 8 and the heavier of the entrained particles are thrown out of the stream and are collected in the hopper 2I2. The air stream then passes from the chamber 2l8 into the chamber H9 and thence into the duct 230. The lighter dust particles drop out of the stream in the chamber H9 and 'are collected in the hopper 240.

In the form of apparatus illustrated the air stream is continuously circulated through the cycle as described but in some cases it may be desirable to provide a by-pass in the air stream circuit leading to a dust filter or arrester whereby to remove very fine solid particles which may not be completely removed from the air stream in the settling chambers. V

The separator illustrated in Figs. .5 and 6 is admirably suited for use in reconditioning abrading material and this separator may be employed in an abrasive reconditioning or cycling system, such as illustrated particularly in Figs. 1 and 2 instead of the form of separator therein illustrated. If desired, means similar to that illustrated and described in connection with the form of apparatus shown in Figs. 3 and 4 may be provided for electrostatically retarding the flow of dust and sand along the table.

From the foregoing it will be seen that the present invention provides apparatus for separating granular material, which apparatus is simple and rugged, which has a relatively small number of moving parts and which can be operated with the expenditure of relatively little power. The separator is efiective in action'and insures a substantially uniform separation of granular material over long periods of operation. In fact, the construction of the separator inherently is such that the effectiveness of the separator remains substantially uniform throughout its life.

The separator ,is relatively compact and is capable of being installed readily in connection with other apparatus as for example, apparatus for recycling or reconditioning abrading material, and when once installed, requires little or no attention or adjustment. The separator substantially is self-cleaning and requires little or no shut-down for cleaning or adjustment. By suitable control and adjustment of the speed of rotation of the table, the velocity of the air stream, the spacing of the gap between the table and skimmer ring, it is possible to provide for considerable variation and adjustment in the operation of the separator to provide for separating articles of variousfsizes and weights. It is also possible to separate the granular material into three or more components. In fact, a substantial number of baifles and'associated hoppers may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. Apparatus for separating granular foreign material from abrading material, comprising a housing, a table within said housing and having an upper surface adapted to permit substantially free movement of granular material thereon, means for depositing granular material on the upper surface of said table, means for rotating said table to effect movement of granular particles across and off said table, means whereby rotation of said table produces an electrostatic charge thereon for retarding the movement of the lighter particles across said table, and means for passing a fluid current through the granular material leaving said table to entrain therein said lighter particles and separate them from the heavier particles.

2. Apparatus for sorting mixed granular abrading material and foreign particles, comprising a housing, a table rotatably mounted in said housing, means for depositing granular material on the central portion of said table, means for rotating said table to efiect movement of the granular material across said table and to eject the same adjacent the periphery of the table, stationary friction means engageable With said table for creating a static electrical charge on said table to selectively retard movement of said gran ular material, and means for passing a fluid current through the granular material leaving said table whereby to entrain in' said current the lighter particles and separate them from the heavierparticles.

3. Apparatus for separating and classifying granular material comprising a housing, a table in said housing having a substantially unobstructed upper surface, means for depositing granular material on the upper surface of said table centrally thereof, means for rotating said table to effect a flow of granular material outwardly and downwardly therefrom by combined centrifugal and gravitational force, means for passing a fluid current inwardly through said granular material leaving said table whereby to entrain in said current the lighter particles of granular material, and baffie means for isolating the gaseous current containing the lighter particles from the remaining heavier particles, said baflie means including an outer circular baflle having an upper free edge spaced from and disposed substantially under the periphery of said table in position to segregate the lighter and heavier falling particles and a plurality of inner baffles positioned inwardlyof said outer baiiie to efiect a tortuous flow of the gaseous current whereby to separate the entrained particles therefrom.

4. Apparatus for sorting-mixed granular material comprising a housing, a main chamber having an inlet therein, a generally circular table mounted for rotation in a horizontal plane, a plurality of generally vertically extending concentric, cylindrical partitions disposed below said table and substantially concentric therewith and defining a series of communicating inner chambers, said table being associated with at least one of said partitions to close the upper end of the corresponding chamber, the outermost of said partitions having an upper free edge disposed adjacent but spaced from the periphery of said table to effect a primary separation of granular material and to provide a gap leading into the chamber defined by said outermost partition, the remaining partitions being disposed to define a tortuous path, an outlet conduit extending from the innermost chamber through the remaining chambers and out of said housing, and means for circulating a current of air through said inlet, said outer chamber, said gap, said inner chambers and said outlet conduit successively.

5. Apparatus for sorting mixed granular material comprising a housing defining a, main chamber having an inlet for granular material and an inlet for a gaseous current, a table mounted for rotation about a vertical axis, means for rotating said table for causing granular material to fall therefrom, a plurality of vertically extending, generally cylindrical partitions disposed in said main chamber below said table and substantially coaxial therewith, said partitions defining a series of inner chambers communicating at their tops and bottoms alternately to define a tortuous path for a gaseous current, the outermost of said partitions presenting an upper edge disposed in spaced relation to the periphery' of said table to provide a gap leading into the upper portion of the chamber defined by said outermost partition, said edge being positioned to effect a primary segregation of the components of granular material falling from said table, one separation component passing throughsaid gap 'and the other passing outwardly of said outermost partition, means for collecting granular material falling from said inner chambers, conduit means leading from said innermost chamber, and means for conducting a gaseous current through said second named inlet, inwardly through said falling granular material and serially through said gap, said inner chambers and said conduit means.

6. Apparatus for sorting mixed granular material comprising a housing defining a main chamber having an inlet for granular material and an inlet for a gaseous current, a generally circular table mounted for rotation about a vertical axis, means for rotating said table to cause granular material to fall therefrom, a plurality of vertically extending, generally cylindrical partitions disposed in said main chamber below said table and substantially coaxial therewith, said partitions defining a series of inner chambers communicating at their tops and bot toms alternately to define a tortuous path for a gaseous current, the outermost of said partitions presenting an upper free edge disposed in spaced relation to the periphery of said table to provide a gap leading into the upper portion of the chamber defined by said outermost partition, said edge being positioned to eifect a primary segregationofthecomponents of granular material falling from said table, one separation component pass-' ing through said gap and the other passing outwardly of said outermost partition, hopper means disposed under and communicating with said inner chambers for freely and continuously collecting granular materialfalling from said inner chambers, conduit means leading from said innermost chamber through said other chambers, and means for conducting 'a gaseous current through said second named inlet, inwardly through said falling granular material and serially through said gap, said inner chambers and said conduit means.

7. Apparatus for sorting mixed granular material comprising a housing defining a main chamber, a table, means mounting said table for rotation in a horizontal plane, said means including a substantially vertical shaft having its lower end terminating adjacent said table, a plurality of generally vertically extending, generally cylindrical partitions disposed in said main chamber below said table and substantially coaxial therewith, said partitions defining a series of substantially unobstructed inner chambers communicating at their top and bottom alternately to define a tortuous path for a gaseous current, the outermost of said partitions presenting an upper free edge disposed in spaced relation to the periphery of said table to provide a gap leading into the upper portion of the chamber defined by said outermost partition, said edge being positioned to efl'ect a primary segregation of the components of falling granular material, one separation component passing through said gap and the' other passing outwardly of said outermost partition, means for collecting granular material falling from said inner chambers, conduit means leading from said innermost chamber out of said housing, and means for conducting a gaseous current inwardly through said falling granular material and serially through said gap, said inner chambers and said conduit means.

DAVID C. TURNBULL. 

